Operation Board Section - Panasonic KX-FT72BR-G Service Manual

5.11. OPERATION BOARD SECTION

The unit consists of an LCD (Liquid crystal display), KEYs, photo interrupters (sensor), and analog switches (for key scan).
The key scan (analog switch control, reading), sensor detection (sensor control, reading) and LCD control are all controlled by
I/O of ASIC (IC1) on the digital board.
ASIC
CN6 CN2
IC1
CN7 CN1
DIGITAL BOARD
5.11.1. KEY SCAN
When CN1(8) (OPSEL) is "H", the analog switch (IC1) is available. The "KLATCH", "KSCLK" and "KTXD" control the analog switch
(IC1) to read at KIN0~3.
Analog Switch (IC1) Control
KLATCH (A)
KSCLK (B)
KTXD (C)
Key Matrix
CN3
ANALOG SW
IC1
READ POSITION SENSOR
DOCUMENT SENSOR
0 1 2
L H L
L L H
L L L
LCD
(Chip on board type)
OPERATION BOARD
KX-FT72BR-G OPERATION BOARD:BLOCK DIAGRAM
3 4 5
H L H
H L L
L H H
133
8X4
KEYS
MATRIX
6 7
L H
H H
H H
KX-FT72BR-G